1. Field of the Invention
This invention relates to methods of applying coatings exhibiting anti-corrosion and/or adhesion-promoting properties to metal surfaces and to metals possessing such coatings on at least a portion of a surface thereof.
2. Description of the Prior Art
Most metals are susceptible to some form of corrosion, in particular atmospheric corrosion, resulting in the formation of various types of rust. Such corrosion may significantly affect the quality of a metal. Although superficial corrosion can usually be removed from metal surfaces, processes for its removal tend to be time consuming, costly and may have a negative impact on the integrity of the metal. Where coatings are applied to metal surfaces, corrosion of the metal may result in inadequate or ineffective adhesion between the coating and the metal surface. A reduction in adhesion between a coating and metal surface to which the coating has been applied may likewise lead to corrosion of the metal.
Metals of many kinds, including metal alloys, metal laminates, metal composites, and, the like, are widely used in manufacturing and construction. Certain types of metal, particularly ferrous metals such as iron and steel, often develop rust during storage and shipment. Rust (also called “storage stain”) is typically caused by moisture which condenses on the surface of the metal there to react with the metal or metal coating on the metal. Rust is aesthetically unappealing and often impairs the ability of the metal to directly undergo subsequent processing operations. Thus, prior to conducting any subsequent processing operations, rust often needs to be removed from the surface of metal and the metal surface treated to prevent rust from reforming. Various methods are currently employed to not only prevent the formation of rust during shipment and storage, but also to prevent the formation of rust after the metal has undergone subsequent processing operations.
It is well known that prevention of rust on metals during their storage, shipping and use can be achieved by applying to their surfaces a thin film such as one of chromate. While chromate coatings do provide resistance to the formation of rust, chromium is highly toxic and environmentally undesirable. Furthermore, a chromium layer may do nothing to improve the adhesion of any subsequent layer applied thereto.
Therefore, a need exists for a method for coating metal that does not utilize chromium while still providing desirable anti-corrosion and adhesion properties.